Electrical capacitors, particularly used as interference suppressors for attenuating noise voltages within the radio frequency range, are often manufactured in one unit by building up alternate layers of metal and dielectric placed one on top of the other. Such capacitor units may contain one, two or three capacitors, usually rolled into so-called capacitor coils. More recently, greater and greater demands have been placed on well-defined frequency properties in the capacitors. Furthermore, similar demands are made with regard to miniaturizing the units as well as fabricating them using automatic production techniques. So far, these demands have only been able to be realized in the fabrication of at most two capacitors in one and the same unit. In fabricating units with two capacitors the metal layers may namely be arranged in the form of metallization on the dielectric, since the electrical connections can be made by metallizing the end surfaces of the coil. Spot connections are therefore avoided while the units may be made very small and manufacture easily automated.
In the production of three capacitors in one and the same unit, the process has so far been that of covering the whole of one side of an elongate insulation film with a metallic film and applying three shorter metallic films at mutual spacing in the longitudinal direction of the insulating film on its other side, the unit then being rolled along its length into a capacitor coil. A capacitor is thus formed between each of the three shorter metallic films and the longer one. Since it is not possible to metallize the end surfaces of the coil in this case, each of the three shorter metallic films must be provided with an individual contact tab, which naturally places particular demands on material thickness and contact ability. Due to the dot contact which the connection tab gives, the frequency properties of these capacitors are deteriorated at the same time as the units will be voluminous and will furthermore not permit automated and cheap manufacture. The manufacturing method with metallization of the ends of the coil has per se been presented for example in EP A2 90170 but this method has given inferior results. The deep cuts made in the coil to part the conducting foils may produce short circuited layers and a burnt dielectric causing severe changes in the electrical data of the capacitor.